THE UNKNOWN DEVIL is a delightfully intriguing and very fast-paced thriller-mystery starring a remarkably likable protagonist {that's become a rarity} who is far beyond my usual sphere, but is eminently empathetic nonetheless. CT Ferguson is an expert computer hacker and coder, university graduate, wealthy enough not to need to work, son of wealthy philanthropic parents. He became a PI after some years in Hong Kong, his empathetic traits and desire to help others as strong as ever. Here he leaps in to rescue another coder genius, who exemplifies feckless victim perfectly. Ransomware, the Baltimore Mafia contingent, and a Mob loose cannon with anger issues and sociopathy also get mixed in, to detrimental results. But our intrepid PI protagonist continues to carry the day and simultaneously endear himself.